A method for manufacturing a semiconductor device with a semiconductor substrate by which an epitaxial film is filled in trenches to form a doped layer having a high aspect ratio is disclosed in Japanese Patent No. 3485081. Further, a method for manufacturing a semiconductor substrate by which an epitaxial film is filled in trenches to form a doped layer when a super-junction structure (P/N column structure) is formed in a drift region in a vertical type MOS transistor is disclosed in Japanese Unexamined Patent Publication No. 2003-124464.
In the above device, a P-type silicon layer as an epitaxial film was filled in trenches of an N-type silicon substrate to form a diode structure. In this case, when a defect (i.e., a void) occurs in the epitaxial film filled in the trenches, a breakdown occurs at an upper portion of the void, which results in reducing a breakdown voltage.
In this manner, the influence of defects in the filled epitaxial film reduces the performance of a device. To be more detailed, the influence of defects reduces the breakdown voltage of the above-described super-junction structure (P/N column structure) and produces crystalline defects caused by filled defects (voids) to reduce a breakdown/junction leakage current yield and leaves resist in the portions of defects in the trenches to cause contamination in the process.